[willamette-fcst] Forecast - Friday, February 13th, 2009

[Willamette Valley Ag/Burning Forecast]

Daily Smoke Management Forecast




Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

Issued: 
     Friday, February 13th, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is allowed.  Suggested burn times are from now until 3:30pm.
     Stack burning is not allowed.

Weather Discussion:
     Light rain moved onshore and into the western valleys
     Thursday night and was already tapering off this morning. 
     Rainfall amounts were around one-tenth of an inch or less,
     with the bulk of the moisture from this latest weather
     system moving south of the region, into California.  Cloudy
     skies and areas of light rain kept valley temperatures above
     freezing overnight with most minimums in the mid 30s.

     The air mass is still quite cold over Oregon.  The freezing
     levels over Salem and Medford were measured at just 2100 and
     1900 feet respectively early this morning.  That puts the
     snow level near 1000 feet this morning.  ODOT road cameras
     showed mostly wet pavement over the coastal mountain passes,
     although packed snow was reported over Sunset Summit, on HWY
     26. The Cascade and Siskiyou paseses were snow-packed, with
     new snow amounts ranging from less than an inch on Mt. Hood
     up to about 4 inches over sections of the southern Cascades
     and Siskiyous.

     The ODA surface analysis put the low-pressure center about
     100-150 miles off the southern Oregon/northern California
     coast, with northeasterly pressure gradients across western
     Oregon.  As the low-pressure center continues to drift
     southeastward, pressure gradients will slowly turn more
     northerly across western Oregon this afternoon.  Transport
     wind directions are not conducive to good valley ventilation
     for stack burning, so it is not allowed today.

     Skies should remain mostly cloudy today, with satellite
     imagery showing an impressive cloud-shield circulating
     around the low-pressure center across all of oregon. 
     However, showers will continue to taper off, with the main
     jet stream energy focused well south of the region.  The
     low-pressure center will weaken and move inland, into
     northern California, tonight.  Partial clearing overnight
     may allow Willamette Valley temperatures to locally drop
     below freezing.  There will still be a slight chance of a
     light shower with the snow level at or below 1000 feet. 

Surface Winds:
     N 5-10 this morning, N 5-10 this afternoon.
Transport Winds:
     NE 8 this morning, NNE 10 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 2000 feet.  Ventilation index 20.
High Temperature:
     Salem\'s high temperature today will be near 44.
Humidities:
     Minimum relative humidity will be near 62%.
Sunrise/Sunset:
     Salem sunset tonight: 5:38pm; sunrise tomorrow: 7:14am.

Extended Outlook:
     A split-flow jet stream pattern is forecast this weekend
     through much of next week.  The southern branch of the jet
     stream, and main moisture feed, will continue to be directed
     into California.   A weak upper-level trough will maintain
     partly to mostly cloudy skies, cool temperatures and at
     least a few showers over Oregon...mainly south. Snow levels
     will rise a little but remain below the Cascade passes.
     Willamette Valley temperatures should remain slightly below normal.

Tomorrow (14 Feb):  Mostly Cloudy.  Slight Chance of a Shower.  Snow Level 1500 Feet. 30/46

Sun (15 Feb):  Chance of Showers and Cool.  Snow Level Near 2000 Feet. 32/46

Mon (16 Feb):  Mostly Cloudy.  Slight Chance of Showers.  Snow Level 2500 feet.  32/48

Tue (17 Feb):  Chance of Showers.  Snow Level 2-3000 Feet.  33/48

Wed (18 Feb):  Slight Chance of Showers.  Snow Level 3000 Feet.  33/50

Thu (19 Feb):  Partly Cloudy.  Slight Chance of Showers.  33/51

Fri (20 Feb):  Partly Cloudy.  Increasing Chance of Showers Late.  33/52

ODA Meteorologist
weather at oda.state.or.us